Service life management system for high-temperature part of gas turbine

ABSTRACT

A life management system for high-temperature parts of a gas turbine has one server system  3  and a plurality of client systems  5   a   , 5   b   , 5   c , and  5   d , all of which are connected via an Intranet. Further, the server system  3  manages a program for performing evaluation of the remaining life and the life management, and each of the client systems  5   a   , 5   b   , 5   c , and  5   d  has a subprogram for accessing the database  4  and for entering data respectively. The clients are dedicated to different objects and share respective element data such as real component damage, design, materials, etc. which are necessary for the evaluation of the remaining life. Further, this system enables the operation of the gas turbine to be optimized based on the damage of the evaluated parts, hence contributing to operational cost reduction of the gas turbine.

TECHNICAL FIELD

The present invention relates to a life management system for partscomprising a gas turbine that reach a high temperature when in use dueto the combustion gas of very high temperature thereof (hereinafterreferred to simply as “high-temperature parts”).

BACKGROUND ART

A combustor, nozzle blades, etc., which are the high-temperature partsof the gas turbine, are located in a channel of the combustion gas of avery high temperature, and therefore may suffer damages, such as thermalfatigue cracking creep deformation etc. which break out due to thermalstrain induced repeatedly in connection with start-ups and shutdowns ofthe gas turbine and a high-temperature environment during its steadyoperation. A gas turbine power-generating unit in which electric poweris generated by driving a power generator with rotational output of thegas turbine has merit of an excellent operability compared to otherpower-generating units.

Therefore, the gas turbine power-generating unit is imposed with severeoperating conditions such as Daily Start-up and Shutdown (DSS) andWeekly Start-up and Shutdown (WSS). Operations, such as these DSS andWSS, where the number of start-ups and shutdowns reaches a large valueare employed frequently. Especially, because the high-temperature partsof the gas turbine are used under extremely severe conditions,heat-resistant superalloys of nickel base or cobalt base are used forthese parts. Although being superalloys, such high-temperature parts areused under conditions close to their critical temperatures, and thatthere is a variation in operating conditions as described above.Consequently, these parts are likely to suffer damages considerablyearlier than other parts.

Therefore, when putting the gas turbine into operation, it isperiodically suspended, parts including the high-temperature parts etc.are inspected for the damages, and if necessary a part is repaired orreplaced. However, since these parts are made of expensive superalloys,costs required to perform their repairing and replacement inevitablyoccupy a considerable portion of an overall operational cost. In orderto reduce the operational costs, it is important to improve the accuracyof evaluation of remaining lives of these parts and hence aim atrationalizing any standards for repairing and replacement.

Regarding techniques for evaluating the remaining life of thehigh-temperature parts, for example, in Japanese Published UnexaminedUtility Model Application No. 4-27127, proposed are a method and itsdevice for estimating thermal strain induced in members from measurementresults of an exhausted combustion gas temperature and estimating theirdamage. For other methods, in Japanese Published Unexamined PatentApplication No. 4-355338, proposed are a method and its device forevaluating the damages by taking in a crack initiation status of amember surface as an image and simulating crack growth using a certainprobability model. Further, in Japanese Published Unexamined PatentApplication No. 10-293049, proposed is a maintenance management devicefor the gas turbine that enables its maintenance by means of damageevaluation based on changes of microscopic structure, and crack growthprediction, etc.

In addition to these contrivances, used is a method wherein a sample istaken out of a part to be inspected and then imposed with a destructivetest to estimate its damage, and the like. Further, in JapanesePublished Unexamined Patent Application No. 10-196403, devised is a lifemanagement device for judging necessity of repairing and replacement ofeach part of the gas turbine based on management of actual data thereofand their evaluated lives and displaying the results.

In applying the above-described methods to a practical use, professionalknowledge and design data such as materials data, results of structureanalysis, etc. are necessary. Further, it is also important to prolong aperiod required for these evaluations in order to reduce operationalcosts necessary for installation maintenance. Further, to improve theaccuracy of the evaluation, it is also important to maintain acircumstance where comparison and referencing of damage data of the pastcan easily be conducted. To do so, it is necessary to construct adatabase with information comprising a base of the evaluation and putthe database into operation. However there is few cases where suchinformation is integrated so as to be served as an available databasebecause a person who installed the gas turbine, person in charge ofmaintenance management, its designer, etc. are different to one another.

Owing to this, frequently it is likely to be a work requiring aconsiderable time in existing circumstances to prepare the damage datafrom results of inspection and evaluate the damage by referring todesign data and material data. There is often the case where worksnecessary for performing, for example, preparation of material datanecessary at time of designing, statistical analysis of real componentdamage data, review of design conditions based on it, etc. becomecomplicated, because databases are not served in such an integrated formthat allows various staff members to share information. To solve thedifficulties, a remaining-life evaluation device and the life managementdevice as described above have been proposed. However, respectivefactors in the evaluation, such as investigation of the damage data of areal component, damage analysis, selection of material data, etc. stillrequire professional knowledge, and hence its effective operation is ina difficult situation.

In addition, although conventional methods enable an operator to obtainthe damage and the remaining life of an object part, it is also animportant task to optimize operation of the gas turbine based on thedamage of a part evaluated, in order to reduce operational costs. Toachieve this, results of the structure analysis when a loading patternat time of start-up and shutdown is altered, material data under acondition where repairing is performed, etc. become necessary. However,with current methods, it is difficult to rapidly formulate bothprediction of the damage and the remaining life when these conditionsare altered and the optimization of operation of the gas turbine withintent to reduce the operational costs consistently.

DISCLOSURE OF THE INVENTION

Therefore, it is the object of the present invention to provide a systemcapable of rapidly performing the remaining-life management of thehigh-temperature parts of the gas turbine.

In the present invention, a remaining-life management system forhigh-temperature parts of the gas turbine is constructed that is capableof using an Intranet and working in that environment.

That is, the remaining-life management system comprises one serversystem and a plurality of other client systems, wherein the serversystem manages a program for performing the evaluation of the remaininglife and the life management, and each client system has a subprogramfor accessing the main database of the server system and entering datathereto.

Further, the remaining-life management system employs such a scheme thatthe results of the structure analysis under conditions where a loadvariation pattern of start-up and shutdown is altered and life data ofrepaired members are saved in a database belonging to the client systemdedicated to handling these specially, and any data necessary for thelife management are transferred to the server system.

Furthermore, a system configuration of a client-server system is adoptedthat enables an organic combination of the damage database such asresults of regular inspection etc., a structure analysis database, amaterials database, etc. so that analytical evaluation of an inverseproblem which is necessary to examine a life extending structure can beperformed rapidly using real component field data.

The life management is performed based on the evaluation of damagegrowth such as a crack in each part. In evaluating the crack growth, itis necessary to set several operating parameters such as the combustiongas temperature, the warming temperature, and the operating time for onestart-up and shutdown, etc. When these parameters change, stress andstrain induced in the members change, and hence the damage growth ratealso changes.

If change of the stress etc. due to the change of an operating parameteris analyzed one by one and the life is evaluated based on the results,it takes a considerable amount of time. To circumvent this problem, thedamage growth is evaluated beforehand under a condition where eachoperating parameter is altered and a relationship between the damagegrowth rate and the amount of alteration of each operating parameter isfound, respectively. From those relationships, a rate of change of thedamage growth rate when each operating parameter is altered is obtainedas an acceleration coefficient or index as compared to that of standardconditions. Using the acceleration coefficients or indexes enable damagegrowth analysis under arbitrary conditions to be performed rapidly.

Furthermore, the above-described acceleration coefficients are set basedon results of the damage analysis using the stress and strain that werefound through the regression analysis of data obtained at a regularinspection of the real component or through the structure analysis underconditions with altered operating parameters beforehand.

Using the above damage growth analysis, it is evaluated whetheroperating parameters can be altered so that the damage growth rate islowered so much as to enable the period of repairing and replacement tobe extended and whether an economic effect can be obtained through thatalteration. In addition, change of the damage growth rate due torepairing and coating application is also evaluated and stored, as isthe case with the above-described acceleration coefficients. Byperforming the above-described damage growth analysis plural times,alteration of a time of repairing, a repairing method, a time of coatingapplication, or a time of inspection that can give the largest economiceffect are judged and displayed within the limit of a predeterminedoperation program (i.e. operational mode such as DSS and WSS, a time ofinspection, etc.).

By the way, when evaluating the effect of coating, in order to considerthe thermal shield effect of coating, a relationship between the stressand strain obtained in the structure analysis under conditions where theheat transfer coefficient of a member surface is changed and the life ofthe member depending upon thermal boundary conditions obtained from thedamage growth analysis, which were stored beforehand, are used.

The evaluation of the damage growth is performed for each part. Resultsof evaluation for each part is shown on an arrangement drawing of eachpart. Thus, a person in charge of device management now can grasp damagesituation of each part easily.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of the remaining-lifemanagement system according to the present invention.

FIG. 2 is a diagram showing flows of data between the server system andclient systems in the remaining-life management system according to thepresent invention.

FIG. 3 is a diagram explaining a concept of an evaluation method that isused in an embodiment of the present invention, with the use of agraphical representation.

FIG. 4 is a cross sectional view of a substantial part of the gasturbine showing arrangement of high temperature parts of the gasturbine.

FIG. 5 is a graph showing the combustion gas temperature of the gasturbine versus time from its start-up to shutdown.

FIG. 6 are graphs showing relationships between characteristic curves oftemperature-strain hystereses for part A and Part B on a first-stagenozzle of the gas turbine and locations of part A and part B.

FIG. 7 is a flowchart for the evaluation of the remaining life and theevaluation of the crack growth.

FIG. 8 is a graph showing a temperature-strain. characteristic curve ofthe first-stage nozzle of the gas turbine under conditions with variedwarming temperatures of the gas turbine.

FIG. 9 is a graph showing a relationship between the damage value andthe warming temperature in a relationship between the damage of thefirst-stage nozzle of the gas turbine and the warming temperature.

FIG. 10 is a graph showing crack growth behavior of the first-stagenozzle of the gas turbine operated in the DSS mode.

FIG. 11 is a graph showing crack growth behavior of the first-stagenozzle of the gas turbine operated in the WSS mode.

FIG. 12 is a graph showing a relationship between crack growth rateversus loading frequency.

FIG. 13 is a graph showing the effect of operating time per one start-upand shutdown on the life.

FIG. 14 is a graph showing a characteristic curve of temperature-strainhysteresis of the first-stage nozzle of the gas turbine when conditionsof coating application are altered as parameters.

FIG. 15 is a graph showing change of the damage value under conditionsof the coating application.

FIG. 16 is a flowchart showing flows for selecting repairing methods inthe remaining-life management system according to the present invention.

FIG. 17 is a graph showing change of the crack growth behavior beforeand after the first-stage nozzle of the gas turbine was repaired.

FIG. 18 is a graph showing a relationship between the life-lowering rateafter repairing and the crack length before repairing on the first-stagenozzle of the gas turbine.

FIG. 19 is a graph showing the crack growth characteristic of repairedmembers.

FIG. 20 is a graph showing a relationship between operating stress andthe crack length of the first-stage nozzle of the gas turbine beforerepairing.

FIG. 21 is a graph showing the difference of the crack lengths of thefirst-stage nozzle of the gas turbine dependent on repairing methods.

FIG. 22 is a flowchart for evaluating the effect of the coatingapplication on the first-stage nozzle of the gas turbine.

FIG. 23 is a cross section of a member on which coating was applied.

FIG. 24 is a graph showing a relationship between the member temperatureof the first-stage nozzle of the gas turbine and the thermalconductivity the high-temperature side.

FIG. 25 is a graph showing a relationship between the operating stressof the first-stage nozzle of the gas turbine and the member temperature.

FIG. 26 is a graph showing a relationship between the life and thethermal conductivity of the first-stage nozzle of the gas turbine, whichis used to evaluate the life extension rate dependent on the change ofthe thermal conductivity.

FIG. 27 is a graph showing an example of evaluation of an optimal timefor coating application and repairing for the first-stage nozzle of thegas turbine.

FIG. 28 is a diagram showing an indication example of damagedistribution in the nozzle ring of the gas turbine.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a configuration diagram of the life management system ofthe gas turbine 1 for a gas turbine power-generating unit. A serversystem 3 acting as a main component of the present system and a maindatabase 4 are located in the center of a network and a plurality ofclient systems 5 a, 5 b, 5 c, and 5 d and the server system 3 areconnected in a manner of the network connection. Each of the clientsystems 5 a, 5 b, 5 c, and 5 d has a browser for accessing the serversystem 3 as well as a computer and a database in compliance with eachobjective.

For example, the client system 5 a used for operations managementcollects data concerning operating states of the gas turbine 1 from themonitoring device 2, transfers necessary data to the server system 3 viaits browser and receives results of evaluation of the remaining lifecorresponding thereto and an optimal system operation schedule from theserver system 3.

At the client system 5 b dedicated to the maintenance, the damage dataof each member obtained at time of regular inspection are enteredthereto, these damage data being exchanged with the server system 3, andjudgments concerning the evaluation of the remaining life of parts andtheir repairing and replacement are performed. The evaluation of theremaining life is done using the following two methods at the same time:(1) an inductive evaluation method wherein a tendency analysis of thedamage growth is performed through analytical processing etc. using thedamage data of members of the past; and (2) a deductive evaluationmethod wherein the stress and strain exerting on the members areevaluated through the structure analysis etc. based on the designconditions and operations data, and based on these results, the crackgrowth analysis is performed by means of, for example, the fracturemechanics and the like.

In the latter, the deductive evaluation, necessary design conditions andmaterial data are transferred from each of the client systems 5 c, 5 dto the main database 4 and the evaluation is performed there, and at thesame time, data processing based on the real component damage data etc.with intent to review the design conditions can also be performed. Forexample, in a thermal stress analysis of the high-temperature parts,thermal boundary conditions (i.e. environmental temperature, the thermalconductivity, etc.) are reviewed so that the results of analysis becomesimilar to a damage distribution of the real component.

In that occasion, results of damage investigation such as a crackingsituation etc. of a certain part, namely a position of crack generationand its length are schematically illustrated on a drawing of the part.Next, the drawing of the part is divided into a plurality of areashaving a suitable size and a contour map of the damage is formed, eachcontour having the same amount of damage evaluated by using the data ofcracking situation, and transferred to the client system 5 c of adesigner. An operator who reviews alteration of design conditions altersappropriately the design conditions such as its thermal boundaryconditions, reviews calculation conditions so that results of the stressanalysis come near to the above-described contour map, and reexaminesthe stress. Its results are transferred to the server system 3 and theremaining life is evaluated there.

Moreover, occasionally when the real component is inspected, a portionof a part is sampled as a specimen and inspected destructively, orwithout sampling a specimen, a part is inspected in a non-destructivemanner, so that deterioration degree of the part is evaluated. Theexperimental results are entered to the materials client system 5 d. Bycomparing the test results with data stored in the materials database 6,the remaining life of the part is evaluated, and the result istransferred to the server system 3.

In the present life management system, the above-described inductiveevaluation method is called as tendency evaluation of the remaininglife, the deductive evaluation method is called as analytical evaluationof the remaining life, and the evaluation method by means ofdestructive/non-destructive testing of the real component or its sampledmember is called as destructive/non-destructive evaluation of theremaining life. Actual evaluation of the remaining life is performed byintegrating these evaluation methods. FIG. 2 depicts data flows in theintegrated evaluation of the remaining life. The damage growth isevaluated by both the tendency evaluation and the analytical evaluationof the remaining life. The tendency evaluation is performed in theserver system 3 after the damage data of the real component weretransferred from the client (#2) 5 b to there. The analytical evaluationis also performed in the server system 3 after the results of thestructure analysis were transferred from the client (#3) 5 c to there.If there arises a difference between the results of both evaluationmethods, the conditions of the structure analysis are reviewed bytransferring data between the above-described client system 5 c and theserver system 3 and the analytical evaluation is recalculated.

Through the above procedures, the evaluation of the damage growth isperformed. In the destructive/non-destructive evaluation, the criticaldamage value is evaluated in the server system 3 based on thedeterioration degree of the material evaluated by the client system 5 d.Using these results, the integrated evaluation of the remaining life isperformed and its results are transferred to the operations managementclient system 5 a. An idea of this evaluation method is illustrated inFIG. 3 with the use of a graphical representation.

In the present life management system, the server system 3 should be arelatively large computer such as a work station; whereas the clientsystems 5 a, 5 b, 5 c, and 5 d are run by standard personal computersthrough Intranet connection, respectively, so that the client system canbe operated without the need for special knowledge.

In the following, shown is an embodiment according to the presentdevelopment with a special emphasis on the nozzles, namelyhigh-temperature parts of the gas turbine. FIG. 4 is a schematicillustration showing a high-temperature gas channel of the gas turbine,where a combustor liner 7 a, a combustor transition piece 7 b, afirst-stage nozzle 8 a, a first-stage moving blade 9 a, etc. are allhigh-temperature parts. Since the first-stage nozzle is located justafter an exit of the combustor, that blade is a part exposed to ahighest temperature in a turbine unit; there have been reported severalcases where thermal fatigue cracks were generated on a surface of thefirst-stage nozzle due to thermal fatigue induced by temperaturevariation of the member in connection with the start-up and shutdown ofthe turbine.

Because of this fact, the first-stage nozzles are being regularlyrepaired and regarded as parts associated with a high necessity ofimproving a remaining life extending technique and the life management.FIG. 5 is a diagram showing one example of variation pattern of thecombustion gas temperature in connection with start-up and shutdown ofthe gas turbine. As an example of the thermal stress analysis of thefirst-stage nozzle of the gas turbine under this condition, the middleand bottom of FIG. 6 show a temperature-strain hysteresis of an end wall(part A) and that of blade trailing edge part (part B), respectively, ofthe first-stage nozzle of the gas turbine shown in the top of FIG. 6. Inthe above-described deductive method, the life of a member is evaluatedusing the result of this structure analysis. An example of theevaluation method is described in the following (1) and (2).

(1) As shown in FIG. 6, a strain range is calculated from the results ofthe structure analysis. A fatigue life N_(f), a life when strain isrepeatedly imposed on a member at the highest temperature in the cycleis obtained and its inverse (1/N_(f)) is referred to as fatigue damageD_(f).

Next, the stress and temperature in the steady operation are obtained.During this period, thermal stress generated in a period from thestart-up to the steady operation is being retained and stress relaxationtakes place through creeping. Behavior of the stress relaxation isestimated by a creep strain formula for the material and creep damage iscomputed by the following formula. $\begin{matrix}{{Dc} = {\int_{1{cycle}}{\frac{1}{t_{R}\left( {\sigma,T} \right)}{t}}}} & {{Equation}\quad 1}\end{matrix}$

Where t_(R) is a creep rupture life, which varies depending on theoperating stress and the temperature. These data are provided from thematerials database and used for the evaluation. In practice, the creepdamage D_(c) per one start-up and shutdown is found as follows: a stressrelaxation curve is obtained; a period of the steady operation isdivided into micro intervals; the creep damage for each interval isobtained in the same form as that of the equation 1; and respectivecreep damages are summed up.

Summation of the fatigue damage and the creep damage both thus obtainedis a damage value for one start-up and shutdown, and the number ofstart-ups and shutdowns at which the damage value reaches an upper limitvalue that was separately given is judged to be the life of the member.Here, the upper limit value is generally determined based on the life ofa specimen obtained experimentally and it corresponds to a crackgeneration life during which the crack develops comparable to thediameter of the specimen. However, in the gas turbine nozzle, it isoften the case that cracks longer than the above-described diameter maybe allowed, and therefore the above method tends to bring aboutexcessively conservative evaluation.

(2) An appropriate initial crack length is set and the fracturemechanics parameters (such as a range of cyclic J-integral, a range ofstress intensity factor, etc.) are computed. Since calculating formulafor calculating fracture mechanics parameters have different formsaccording to shapes of members, modeling techniques for cracks, etc.,calculating programs corresponding to several typical models are beingstored in the system. Here, suppose that, for example, an iterativeintegration J_(f) is computed by one of the programs. Then, the crackgrowth rate is computed by the following formula.

da/dN=C(ΔJ _(f))^(m)  Equation 2

This crack growth rate can be considered to be the amount of crackgrowth for each one of start-up and shutdown, and therefore a sum of theinitial crack length assumed and this amount becomes a crack lengthafter one start-up and shutdown. Then the initial crack length issubstituted with the amount thus obtained to find a subsequent cracklength. By repeating the similar calculation, the crack growth can bepredicted. In this case, the life is regarded as a number of start-upsand shutdowns by which the crack length reaches a certain limit length.

When the above-described technique is applied to a practical case, avariation speed of the gas temperature at time of start-up and shutdown,effects of an environment in use, etc. must be considered. To find thesedata experimentally, it is necessary to conduct a number of experimentsand it is often the case that each experiment is difficult to be carriedout under conditions embracing the real component conditions.Consequently, in the analytical evaluation of the remaining lifeaccording to the present system, the damage is evaluated according toflows shown in FIG. 7. The damage under objective conditions isevaluated, for example, by first evaluating the damage under standardconditions, such as design conditions etc., and then introducingcoefficients and indexes representing effects of factors affecting thelife as acceleration coefficients of the damage growth rate.

D₀ and C, m shown in the damage analysis program of FIG. 7 are damagevalues or coefficients or indexes of a crack growth characteristic underthe standard conditions, and coefficients K₁, K₂, . . . , C₁, C₂ arecoefficients representing the effects of respective factors. Thesecoefficients are obtained using experimental data, data of the structureanalysis performed with varied factors as parameters, and the realcomponent damage data, and stored in the main database 4. Operationhistory data and damage history data shown in FIG. 7 are transferredfrom the monitoring device 2 and the maintenance client system 5 b tothe server system 3. Further, necessary material data are transferredfrom the main database 4 to the server system 3. The evaluation isperformed using these data according to flows shown in FIG. 7.

A derivation method of the above-described coefficients K₁, K₂ . . . ,C₁, C₂ , etc. is explained below. By way of example, FIG. 8 showsresults of the structure analysis performed with varied warmingtemperatures T_(w). It is expected that decreasing the warmingtemperature lowers generated strain at time of start-up and delays thecrack growth. Based on results of this analysis, the damage growth rateis obtained by the same method as that of the analytical evaluation ofthe remaining life and a coefficient representing an effect of thewarming temperature is evaluated. In practice, in order to associate thecoefficient with the real component data, the coefficient is determinedin such a manner as shown in FIG. 9.

FIG. 9 shows a graph with a horizontal axis for the warming temperatureand a vertical axis for the damage value, where a solid line in thefigure represents a relationship between the warming temperature and thedamage that was obtained by the above-described method (1) or (2) fromthe result of the structure analysis. In the figure, the damage dataobtained for the gas turbine with different warming temperatures areplotted and the results of the analysis are reviewed so that the datathus obtained and the above-described solid line are consistent witheach other within a certain rage of error. Regarding the operating timeper one start-up and shutdown, behaviors of the damage growth observedin the real component are shown in FIG. 10 and FIG. 11, which indicatethat the damage growth considerably depends upon the operating modes,such as DSS, WSS, etc.

From this fact, the effect of the operating time can be presumed in thelight of a relationship between the crack growth rate and the loadingfrequency, for example, shown in FIG. 12. FIG. 12 is obtained from theresults of a crack growth test of the nozzle member. Since the loadingfrequency can be considered as an inverse of the operating time per onestart-up and shutdown, reduction of the load frequency means that aperiod from start-up to shutdown becomes longer. By deriving anapproximate equation for these data, a coefficient representing aneffect of the operating time can be obtained. The coefficients obtainedfrom FIG. 12 can be applied, as it is, to the above-described damageevaluation method (2); whereas in the case of the method (1), these areapplied in a such manner that the relation between the life and theoperating time per one start-up and shutdown, as shown in FIG. 13, isobtained from the results of the crack growth analysis using thesecoefficients and then the relation is formulated.

In practice, since factors other than the warming temperature affect therelation, the real component data plotted in FIG. 9 and FIG. 12 exhibitensembles with a very large variance. Therefore, with respect to each ofall factors that should be considered, the same graph as FIG. 9 isprepared and the regression analysis is performed. That is, data fittingis performed with varied coefficients and indexes included in respectivecalculating formulas for coefficients of each factor (k₁, m₁, c₁, etc.in FIG. 7), and the coefficients and indexes are determined so that theresults of evaluation fall in a certain given range.

In the foregoing, described is an embodiment for a case where the damageof a part currently in use is evaluated; whereas for a case where thelife extension of each part is examined using the present lifemanagement system, an embodiment for computing the effect is describedbelow. FIG. 14 shows the results of a case where the thermal stressanalysis is performed under the conditions where the thermal shieldcoating is applied on the member surface and generated stress is found.From the analysis, the coating reduces the member temperature, hencealso reducing generated stress. Corresponding to this result, FIG. 15shows results of the damage evaluation that was performed in accordingto the evaluation method described above in (1). The results indicatethat the coating application reduces the creep damage to approximately60% of the initial value. From this result, it is judged whether thecoating application should be executed or not in the light of which issignificant, the amount of cost reduction by parts life extensionachieved by coating or cost increment imposed by coating.

In practice, not only the coating but also the repairing, alteration ofa start-up and shutdown pattern, etc. are considered to be a lifeextension method. FIG. 16 shows its evaluation flows included in thepresent system. Flows until the remaining life evaluation device 10 arethe same as described above and the evaluation is performed in theserver system 3 based on the results of inspection which were entered inthe maintenance client system 5 b. Based on the results, at a time whenthe repairing is required, several repairing methods are considered ascandidates, and the life extension rate and necessary costscorresponding to a case where one of the candidates and the thermalbarrier coating (TBC) are applied are judged by the judgment devise 11for long-life achieving technique using the database 12 pertaining torepairing methods.

This database 12 and the judgment device 11 are included in the maindatabase 4 and the server system 3. As a result of its judgment,considering also the remaining life at a scheduled time of replacement,a repairing method and a time of repairing that can minimize operationalcosts per unit time are selected and transferred to the operationsmanagement client system 5 a, respectively.

As for data contained in the database 12 pertaining to repairingmethods, there are, for example, damage growth data such as a crack of arepaired member which was used actually in the real component, as shownin FIG. 17, etc. and the life lowering rate of the repaired memberobtained experimentally. If modification of the life lowering rate dueto repairing does not depend on the amount of repairing, the value issaved as it is; if it depends on the amount of repairing, with intent tosimplify the evaluation on and after this procedure, a relationshipbetween the amount of damage, such as a crack length before repairingetc., and the life lowering rate after repairing is saved, as shown inFIG. 18.

Furthermore, as for the crack growth characteristic, relationshipsbetween fracture mechanics parameters for respective repairing methods(cyclic J-integral etc.) and the crack growth rate obtainedexperimentally, as shown in FIG. 19, are saved. By substituting data ofthe parent member with data of these repaired members and performing theabove-described evaluation method (1) or (2), the remaining life of ahigh-temperature part that was repaired is evaluated.

As for estimation of a stress value that is necessary in performingevaluation, analysis with varied operating stress is performedbeforehand and the results obtained is saved as a relationship betweenthe operating stress and the crack length at the same number ofstart-ups and shutdowns, as shown in FIG. 20. Then the operating stressis estimated from the crack length at time of repairing. This procedureis taken to enable a simple and easy evaluation by obtaining suchrelationships separately, because it is realistically impossible toconsider the variance of the damages for each one of parts mounted onthe real component.

The operating stress thus estimated is used for the crack growthanalysis after repairing. FIG. 21 shows its evaluation method, in whichhow the crack length will change by the operating stress after thenumber of start-ups and shutdowns that are scheduled just afterrepairing until a next regular inspection or replacement is obtained byperforming the crack growth analysis using the relationship of FIG. 19.By providing the operating stress obtained in FIG. 20 to this finding,the amount of the crack growth when each repairing method is applied isestimated. From the results, which repairing method should be applied isjudged.

The effect of the coating application is evaluated in different flowsfrom that of repairing, as shown in FIG. 22, because the temperature ofa member after the coating application is varied from the initial value.The life computer 13 is a device for performing similar arithmeticexecution as a damage analysis program of FIG. 7. Data to be entered tothe life computer 13 are provided from the database 14 whose data wereformed based on the results of the structure analysis with variedthermal boundary conditions. This database 14 is composed of the resultsof the structure analysis performed by the design client system 5 c andis stored in the main database 4 through the server system 3. The lifeevaluation is executed by the server system 3 and its results aredisplayed as the life extension rate. Considering the costs as wellthis, a time of coating application and a part to be applied withcoating that minimize the operational costs per unit time are determinedin the same manner as of the case of repairing.

Since, in the structural analysis for computing the data to be enteredto the thermal boundary condition-operating stress database 14, it takesa considerable time to perform the structure analysis actually bymodeling a extremely thin coating layer on the member surface, thethermal shield effect of the coating is substituted with the change ofthe heat transfer coefficient to perform the computation by thefollowing method.

FIG. 23 shows a typical diagram of the cross section of the coatingmember. From the heat conduction calculation, the heating value passingthrough the cross section is given in the following formula.$\begin{matrix}{Q = {\frac{1}{\left( {\frac{1}{h_{gas}} + \frac{l_{c}}{\lambda_{c}}} \right)}\left( {T_{gas} - {Tm}} \right)}} & {{Equation}\quad 3}\end{matrix}$

Symbols l_(c) and λ_(c) are the thickness and the thermal conductivityof the coating layer, respectively. From this formula, the coating layercan be treated as a heat transfer boundary equivalent thereto by thefollowing formula. $\begin{matrix}{\frac{1}{h^{\prime}} = {\frac{1}{h_{gas}} + \frac{l_{c}}{\lambda_{c}}}} & {{Equation}\quad 4}\end{matrix}$

A symbol h′ that can be obtained by changing l_(c) and λ_(c)appropriately is used to perform the thermal stress analysis, and theeffect of the coating on the generated stress is evaluated by thestructure analysis. The results are saved in the database 14, as shownin FIG. 24 and FIG. 25, in the form of the relationship between themember temperature and the heat transfer coefficient and therelationship between the operating stress and the member temperature.These relationships differ depending on a part, and therefore data areaccumulated for every part where the evaluation is necessary.

On the basis of these relationships, the crack growth analysis when theoperating stress decreases is performed with the above-describedevaluation method (2), the relationship between the crack growth lifethus obtained and the heat transfer coefficient is obtained for eachpart beforehand as shown in FIG. 26, and the life extension rate bycoating is evaluated by using this relationship.

Considering the evaluation of the life extension rate mentioned above aswell as the costs, it is judged whether the coating application iseffective or not. A computer 15 for that purpose also exists in theserver system 3, which performs the evaluation by obtaining the datafrom the costs database 16 recorded in the main database 4. An exampleof its evaluation is shown in FIG. 27. By the way, as for the selectionof a repairing method, the evaluation is performed based on the sameidea as in FIG. 27. When the gas turbine is put into operation with agiven interval of repairing, if the damage values such as the crack etc.are estimated not to exceed the limit values in each period of time fromrepairing to repairing as in FIG. 27(a), it is judged that the coatingis unnecessary. However, if it is estimated that the life can be securedwithout applying the repairing one time by virtue of the life extensionachieved by coating as shown by the broken line, a content indicatingthis is displayed.

If the interval of the repairing is fixed, the evaluation is completedwith this. If the interval is alterable, the damage growth analysis fora case where the coating is applied at the scheduled time of repairingis performed, as shown in FIG. 27 (b)(c), and an optimal time ofrepairing under the conditions is found. In practice, similar analysisfor cases where different repairing methods are applied is performed, sothat damage growth curves shown in FIG. 27 become available for alloperation schedules considerable.

From these results, the total cost is calculated by summing the costsnecessary for repairing and coating and the remaining life at time ofreplacement that is converted into a cost, and the total cost is dividedby the operating time to find a total cost per unit time. Severaloperational schedules are provided in ascending order of the total costper unit time, so that an operations manager of the gas turbine nowjudges which schedule to adopt based on it.

In a real component, a plurality of the same parts are used in a singlegas turbine simultaneously and their damage growth rates may vary.Therefore, the damage inspection is performed for all parts and theirdata are collected. The results, for example in the nozzle, aredisplayed as a ring distribution diagram as shown in FIG. 28, whichcorresponds to an actual arrangement diagram of the parts, wherein thedamage of each part is indicated with a color or a numeral according toits degree. In this diagram, a part light-colored corresponds to a parthaving non-serious damage; whereas a part dark-colored corresponds to apart having serious damage, and darker the color more serious thedamage.

Further, a predicted damage value after being operated for a certainperiod is also displayed in this diagram and a part that needs therepairing and the coating application is displayed with a time for these(not shown in FIG. 28). Based on this result, parts to be repaired orthe like are specified. This procedure decreases the amount of worknecessary at time of repairing, hence contributing to cost reduction.

If this life management system is adopted, a period necessary for theevaluation can be cut down, because each element data necessary for theevaluation of the remaining life, such as real component damage, design,materials, etc., are shared among different clients dedicated todifferent purposes. Further, operations now can be optimized based onthe damage of the parts that are evaluated, hence contributing tooperational cost reduction.

INDUSTRIAL APPLICABILITY

The life management system according to the present invention finds, asa field of utilization, the life management of high-temperature parts ofthe gas turbine.

What is claimed is:
 1. A life management system for high-temperatureparts of a gas turbine which manages lives of parts composing the gasturbine and being arranged in a channel of combustion gas thereof,wherein: the life management system comprises client systems, each ofwhich is dedicated for each one of operations management, maintenance,design, and material data of the gas turbine; and a server system thatintegrates these client systems and manages a database for a wholesystem; wherein each of the client systems is set to have a function forperforming access and entering data to the database, the server systemsaves a program for performing analysis necessary for the lifemanagement, and each of the client systems and the server system areconnected via an Intranet.
 2. A life management system forhigh-temperature parts of a gas turbine according to claim 1, whereinthe life management system is equipped with means comprising: a devicefor monitoring an operation pattern of the gas turbine; a database forstoring relationships between the operating parameters of the gasturbine and damage or damage growth rate of the parts of the gasturbine; and a computer for analytically predicting the damage growth ofthe parts from the monitored operation pattern, wherein the meanscomputes coefficients and indexes representing effects of the operatingparameters on the damage growth rate according to both damage data ofthe parts and operation history of the gas turbine, performs arithmeticexecution by applying these as acceleration coefficients for the damagegrowth to the damage growth analysis that is executed by the computer,and computes and displays damages and the remaining lives of the partsor the amount of damage at time of next inspection.
 3. A life managementsystem for high-temperature parts of a gas turbine according to claim 2,wherein the parts damage database of the gas turbine stores coefficientsand indexes representing the lives or the crack growth rates of partsunder the operating parameters of the gas turbine through the regressionanalysis using the relationship between the number of start-ups andshutdowns and the damage of the part in the gas turbine under differentoperating conditions, and these coefficients and indexes can be freelyfetched and used when evaluating the damage.
 4. A life management systemfor high-temperature parts of a gas turbine according to claim 2,wherein the life management system is equipped with means for computingthe life extension rate of each part by analyzing sensitivity of thecrack growth to alterable operating parameters; and means for computingalteration of operating parameters or alteration of operation schedulethat minimizes the remaining life at a scheduled time of partsreplacement for a given operation schedule.
 5. A life management systemfor high-temperature parts of a gas turbine according to claim 2,nwherein the parts damage database of the gas turbine storescoefficients and indexes representing effects of each of the operatingparameters on the part life or the crack growth rate that was obtainedbeforehand by analyzing the damage growth of the part based on changesof operating stress exerting on the parts of the gas turbine, strain,and the temperature when each operating parameter is altered, and thesedata can be freely fetched and used when evaluating the damage.
 6. Alife management system for high-temperature parts of a gas turbineaccording to claim 2, wherein the life management system has a databasepertaining to repairing methods corresponding to damage occurring in apart in use as well as the life extension rate and costs when one ofthese repairing methods is applied, and means for judging a repairingmethod that satisfies requirements concerning a given operation scheduleand costs corresponding to the damages of the parts of the gas turbineusing the data of the database.
 7. A life management system forhigh-temperature parts of a gas turbine according to claim 2, whereinthe life management system is equipped with means for obtaining arelationship between a time of inspection of the part of the gas turbineand the damage of the part with a computer for analyzing the crackgrowth and judging and displaying a time of inspection that minimizes acost per unit operating time by using the life extension rate when therelationship and each repairing method are applied, and a databasepertaining to costs.
 8. A life management system for high-temperatureparts of a gas turbine which manages lives of parts composing the gasturbine and being arranged in a channel of combustion gas thereof,wherein: the life management system comprises client systems, each ofwhich is dedicated for each one of operations management, maintenance,design, and material data of the gas turbine; and a server system thatintegrates these client systems and manages a database for a wholesystem; wherein each of the client systems is set to have a function forperforming access and entering data to the database, the server systemsaves a program for performing analysis necessary for the lifemanagement, and each of the client systems and the server system areconnected via an Intranet, wherein the life management system isequipped with means comprising: a device for monitoring an operationpattern of the gas turbine; a database for storing relationships betweenthe operating parameters of the gas turbine and damage or damage growthrate of the parts of the gas turbine; and a computer for analyticallypredicting the damage growth of the parts from the monitored operationpattern, wherein the means computes coefficients and indexesrepresenting effects of the operating parameters on the damage growthrate according to both damage data of the parts and operation history ofthe gas turbine, performs arithmetic execution by applying these asacceleration coefficients for the damage growth to the damage growthanalysis that is executed by the computer, and computes and displaysdamages and the remaining lives of the parts or the amount of damage attime of next inspection, wherein the life management system has adatabase pertaining to repairing methods corresponding to damageoccurring in a part in use as well as the life extension rate and costswhen one of these repairing methods is applied, and means for judging arepairing method that satisfies requirements concerning a givenoperation schedule and costs corresponding to the damages of the partsof the gas turbine using the data of the database, and wherein the lifemanagement system has either of means for judging whether a cost perunit operating time is reduced by applying the thermal barrier coatingand means for finding a time of coating application that reduces thecost, both means being driven with the use of a group of datacomprising: data of the amount of reduction of the stress versus thetemperature when thermal shield coating is applied on a member surfaceof the part of the gas turbine that is obtained through the structureanalysis with varied thermal boundary conditions; data of a lifeextension rate attained by the thermal barrier coating that is obtainedthrough the damage growth analysis based on the amount of reduction ofthe stress; and data of costs pertaining to the thermal shield coating.9. A life management system for high-temperature parts of a gas turbineaccording to claim 6, wherein the database is a database for storing, asdata, a relationship between the damage before repairing, which wasobtained experimentally or through the damage growth analysis, and thelife lowering rate after repairing, wherein the data can be fetchedfreely from the database as data to be used in performing the lifemanagement of the part.
 10. A life management system forhigh-temperature parts of a gas turbine according to claim 8, whereinthe database is a database for storing, as data, relationships betweenthermal boundary conditions, such as the heat transfer coefficient, theboundary temperature, etc., and induced stress and the lives of membersparts, that was obtained by performing the structure analysis aftersubstituting the thermal shield effect of the thermal barrier coatingwith a change of the thermal conductivity, wherein the data can befetched freely from the database as data to be used in performing thelife management of the part.
 11. A life management system forhigh-temperature parts of a gas turbine according to claim 1, whereinthe life management system is equipped with means for displaying anarrangement diagram of the parts of the gas turbine, at the same timedisplaying the damage and the remaining life of each part on thearrangement diagram, and further judging and displaying importance ofthe damage investigation of each part from forecasted damage at ascheduled time of a next inspection according to a criterion givenbeforehand.